Characteristic changer and linear potentiometer



1953 J. J. WILENTCHIK 2,662,149

CHARACTERISTIC CHANGER AND LINEAR POTENTIOMETER Filed May 9, 1950 IN EN TOR.

V JERZYJ; W/L fNTCH/K.

ATTORNEY 10165 drilled alts Patented Dec. 8, 1953 umreo ears-NT OFFICE ciiAitAcTERIsTIc CHANGER I'AND LINEAR POTENTIOMETE-R Jerzy J. Wilentchik, York, h. 3?.

Application May 9, 1950 Seiial Noe160881 7 Claims. (01. 1261-56) 1 This invention relates to improvements in voltage and in position control systems compr sing primary control means. wherein the output y-can-h-e-variedasa function of the displacement ic oftheprimary control means according to-anydesired-function y=f(:v) and is a continuation in part of -my co-pending application,

seriairro. 155, 864 filed on April 14, 1950. I

An object of the 'inventionis to provide a system of the aforementioned character in which the output y expressed as a voltage function is composed of a large *huiiiher of straight line sectors located ina plane :cy, the location and the slope of said sectors being determined individually and set into the instrument in such new; a better iil'id'erstaiidiiig "(if the invention, its advantages ever the szistmgi art and the speand ob ectives attained 'With its use, reference shot-11d beliad to the roilowmg' d'escnptioh and accom anyin drawings in Which preferre embodimentsof the invention have been illustrated and described.

In the drawings? Fig. 1 is a sectional new or the instrument according to the invention. 7

"Fig; 2 is a view of disc 'siippoiti'riigtlie interpolating resistor".

' Fig. 3 is a diagrammatic"representation or a unit control system according to; the invention.

.Fig'. 4 is a; part ybroken sectionai view or a modification of the interpolating resistor providedlw'itli' spring loaded taps. Y

Referring first Fig. 1, t "ere is shown a hellcal, mum-turn groove 3, ar Ig'd along the e35- ternai per hery ora ylih'd 1,.nofi-ddhdfibtifig mandrel 2, a resistance wife 4 being arranged within and along the length ofthe former. The Wire "4, referred to as'the selective resistdr, flakes tli respective coria pressure' electrical contact tact; pins 5 (only (in 'o f the latter" being slidwh If! Fig. I). Thefcdntact Bare inserted V Y l'ectd locations of the g rodve3. Eacli contact pin is connected to a respective ing or by other suitable -rnethods. screws 1 are adapted-to bescrewed into respective connected spring contacts Hi being adaptedtto 'cooperate with the resistance 'conta'ctscrew l by means of a conductor-6. The

electrical connections hetween respective screws 'l-,-com:luctorsc andpins 5 can be-made by solder- The contact tapped holes 25 in a non conducting disc I2, the-holes 25 be'ing arranged at a uniformsdistance from each other, or at predetermined locations alcng the periphery of the disc 12,;this being shownmore-clearly With-reference'to Fig.2. The screws 'lmake an electrical contact with a resistance wire;8;-rcferred to as the interpolating resistor and wound helically on a circular; heavily.

insulated copper core cemented within acircular groovein the disc 12.

Ina modification-of the arrangement shown in Fig. 2, sprin'gloaded taps shown in Fig. 4 have been used. In this arrangement &a disc 121i is provided with a plurality of holes 38 arranged in a circle at'selected locations of its external periphery. The diameter of ahole 36 is sufiiciently large to allow insertion within of a respective :contact tip 370; madeof suitable conducting material and adapted to cooperate 'conductively with, a resistance wire ca, the latter being wound -helica-lly on a heavilyir'isulated copper corecementedwithin a circular groove inthe disc 12a. To produce an adequate spring loading effect between the tips 31a and the wire 8a, a circular non-conducting disc 38 is coupled to the disc-[2a byjmeans of screws 39 andadapted to exert pressure on respective springs 31b by virtue of having a larger radius than the radius of the circle at which the centers of respective -holes:36 arelocated. The spring 3117, the tip Blaand an externarconduct-oriia can be connected together by soldering; by pressure; or can: be made out of one shownin Fig; but seen *inFi'gnI) via respective conductors 6a.-

Referring back to Fig: 1- a contact disc 13 is adapted to be'displaced by means of a control shaftw. The disc 13 carries a pair of intert0 and H, the contact 8 and the contact H wit-h e; collector ring 9, the latter being inserted in a non-conducting end plate I 5. The plate l5supports-azloushinglfi and a bearing Hand-can be fastened by means of a nut it to a stand 18. The collectorring -9 is connectedby means of a conductor 21 to an output terminal 26. At the other end of the mandrel 2, there is provided an end plate 2|, a bushing 22 and a bearing 28 to support the shaft 20. The plate 2! is fastened to a stand 23 by means of a nut 24. Both the stands 23 and is are coupled to a base plate 29 by means of screws 36. The ends of the resistance wire 4 are connected by means of conductors 3i and 32 to a suitable source of voltage 33. For applications requiring a continuous rotation of the shaft 20, the resistance 8 can be of continuous mechanical rotation type having a small gap between the winding terminals.

The contact device l6 being displaced by the control shaft along the periphery of the interpolating resistor 8 interpolates linearly between respective potentials of a pair of taps between which it is situated and reproduces the desired function.

By rotating the shaft 20 continuously in one or in the other direction, at a desired speed of rotation, shaped voltage pulses of desired form and frequency can be produced.

In a specific instant of a sine function potentiometer, by substitution in place of a single contact I!) a pair of contacts (not shown), adapted for simultaneous displacement in conductive engagement with the interpolating resistor 8 and being 90 degrees apart from each other, the functional potentiometer can perform the function of a resolver and produce a simultaneous sine-cosine voltage wave output. A pair of collector rings connected to respective output terminals are of course provided in this arrangement.

For laboratory and other applications, instead of fixed contact pins 5, attachable contacts could be used, adapted to be attached to the resistance wire 4 at any desirable point thereof. In such applications the form of the groove 3 would be that of a T. The attachable contact consists generally of a flanged holder adapted to be inserted manually within the T groove and a spring loaded contact cooperating conductively with the resistance wire 4. Modifications of this arrangement have been described in my co-pending application Serial No. 155,864 filed on April 14, 1950 and are therefore not discussed at length herein.

It will be understood, that instead of a helical resistance 4 arranged in a grooved mandrel 2, a

conventional, circular resistance winding, ar-

ranged in a manner substantially similar to arrangement of resistor 8 could be used and provided with a plurality of selectively located taps.

In the following section of the specification there is described a method of compensation for current take-off by the interpolating resistor.

Let me consider two cases in which the resistance between a pair of successive taps has been referred to as resistor-sector.

In case 1, the resistance of respective sectors of the interpolating resistor is assumed to be infinite, subsequently no current flows in the interpolating resistor and the potential distribution along the length of the selective resistor is linear.

Assuming that the voltage drop between two successive taps on the selective resistor is desired to be us, it being the voltage input to the instrument, the taps would have to be spaced at a distance of (us/10R from each other, R being the total resistance in the selective resistor, said distance being expressed in ohms.

In case 2, the resistance of the interpolating resistor is of a finite value. Subsequently, current flows in the interpolating resistor and the linearity of potential distribution along the selective resistor is destroyed. To realize a voltage drop of us (same voltage drop as in case 1), between two successive taps on the selective resistor, the taps will have to be placed at a distance Rs (in ohms). Calling Ta the resistance of a sector of the interpolating resistor in parallel with Ra, the linearity condition can be expressed in the following form:

R2 (Tia/1L fa- (mi/u.) R

when compared to the resistance of a corresponding sector in case 1, therefore the total resistance of the selective resistor in case 2 will be higher than in case 1. This increase of resistance in the selective resistor can be realized easily by providing additional turns of wire on the helically grooved mandrel 2 in Fig. 1.

It will be noted that the potential distribution along the selective resistor is dependent on the rate of change of the simulated function, and that the location of a tapping point from which a potential of a predetermined magnitude has to be obtained will vary as a function of location of preceding taps on the selective resistor.

Assuming that the tapping points along the interpolating resistor are spaced at an even distance from each other, a table can be prepared for predetermined, constant values of Ta and of R from which the values of Re. can be obtained directly as a function of ua/u. us/u is the slope of respective sectors of the simulated voltage function.

This may find application in laboratory type of instruments mentioned above, wherein the operator will avail himself of such a table when setting in a desirable function form. It is of course understood that at least one terminal of the source of input voltage is designed as an attachable contact and adapted to be shifted along the length of the selective resistor winding so as to accommodate for different function curvatures.

The only design modification required in this arrangement relative to arrangement shown in Fig. 1, is that respective conductors 6 will be brought outside through suitable apertures in the mandrel 2 or in the disc 2| for external connection with the selective resistor 4 instead of being connected to it internally.

The purpose of the system shown in Fig. 3 is to control the displacement of a motor driven load as a desirable function y fla') of displacement x of the control shaft 20. The system incorporates a vari-function potentiometer 35 at the control point, which has been described fully in the preceding section of this specification and a linear potentiometer 50 at the controlled point.

The output contact devices 19 and SE of varifunction potentiometer 35 and the linear potentiometer 59 are connected to respective input terminals 92 and 93 of a combination voltage and polarity sensing power amplifier 99, the latter being of any conventional or commercially available type.

In a balance condition of the system, the potential magnitude of the contact will equal that of the contact 9!, but for a condition of unbalance the voltage applied to the voltage amplifier 90 can be in phase or 180 degrees out of phase with the line voltage considered as a reference.

In general the polarity of the error voltage depends on whether the ratio of the mechanical input at to the changer and of the electrical output y from the linear potentiometer all is higher or lower than that determined by the function y=f(:c). This relationship provides the means following amplification for driving the balancing motor 94 in the proper direction of rotation to rebalance the control circuit.

The balancing motor can be a two phase, reversible induction motor having two separate windings, one winding being connected to the output terminals of the amplifier 90 and the other winding through condenser 98 and a transformer 91 to the a. 0. Voltage supply legs. The

motor 94 will rotate in one sense or the other or remain stationary, depending on. whether the error voltage is positive, negative or zero, re spectively.

If the error voltage is zero, the current output of the amplifier 99 is composed of two actual pulses for each cycle of the supply voltage tending to drive the motor unit 94 in one direction on one half and in the opposite direction on the other half cycle and resulting in no motion of the motor. If the error voltage is positive (in phase with the voltage source) the current output from the power amplifier will be composed of pulses in phase with the positive pulses of the voltage source.

If the error voltage changes signs, the supply current to the motor will be shifted 180 degrees in phase, and the motor will reverse its sense of rotation.

The speed of the motor 94 in either direction depends on the magnitude of the error voltage and decreases as the error voltage decreases.

It will be understood from the foregoing explanation that the motor 94 displaces the contact 9| in conductive engagement with the potentiometer resistance in such direction that tends to decrease the error voltage until it becomes zero, upon which the motor is stopped. The motor 94 drives a load (not shown) which can be any position controlled object.

For monotonic functions y=f(;c), (the slope remains positive or negative throughout the entire range), the respective location of the changer and of the linear potentiometer could be reversed without affecting the performance. In such an arrangement, the linear potentiometer would be controlled manually and the changer by means of a motor unit.

While the invention has been described with reference to certain embodiments, it should be I borne in mind that it is applicable not merely to resistance elements, but to all types of variable voltage sources comprising voltage division means provided with tapping points from which voltages of different magnitude, phase, frequency, etc. may be obtained and applied selectively to voltage interpolating means.

What I claim as novel and desire to secure by Letters Patent is:

1. In a functionally adjustable, variable resistor, in combination, a mandrel, a wire of appropriate resistivity disposed along the length of said mandrel, a plurality of contact elements, interlocking means common to said mandrel and to said contact elements to maintain said elements in. electrical engagement with said wire at any point along the length of said wire, means to manually adjust and readjust said contact elements along the length of said wire, resistance means, conductor means connecting said contact elements to points located selectively on said resistance means, and wiping means adapted to be disposed along the length and in conductive engagement with said resistance means.

2. In combination, a mandrel, a plurality of selectively located holes in said mandrel, a corresponding plurality of contacts disposed in said holes, a resistance winding and spring means to maintain said contacts in conductive engagement with said winding.

3. The combination according to claim 2, including a wiping means adapted to be disposed along the length of said winding and control means to move said wiping means.

4. In combination, a resistance winding, a support for said resistance winding, a plurality of selectively located holes in said support in the plane of said winding, a plurality of contacts disposed in respective ones of said holes in conductive engagement with said winding, a plurality of helical springs in respective ones of said holes to maintain said contacts in conductive engagement with said winding and wiping means displaceable along the length of said winding.

5. In combination, a resistance winding, a

support for said resistance winding, a plurality of selectively located holes in said support in the plane of said winding, a plurality of contacts disposed in respective ones of said holes, a plurality of spring elements disposed in respective ones of said holes to maintain said contacts in conductive engagement with said winding, plug means to lock said contacts and said spring elements in respective ones of said holes and wiping means displaceable along the length of said winding.

6. The combination according to claim 5, wherein said plug means comprises a plurality of metallic lugs in conductive engagement with respective ones of said spring elements.

7. The combination according to claim 6, including resistance elements connected between respective ones of said lugs.

JERZY J. WILENTCHIK.

References Cited in the file Of this patent UNITED STATES PATENTS Number Name Date Re. 18,521 Sachse July 12, 1932 362,859 Stearns May 10, 1887 794,983 Howell July 18, 1905 1,038,342 Gaylord Sept. 10, 1912 1,450,919 Harris Apr. 10, 1923 1,744,592 Terpening Jan. 21, 1930 1,964,846 Earnshaw July 3, 1934 2,113,436 Williams Apr. 5, 1938 2,122,370 Harrison et a1. June 28, 1938 2,221,977 Lannerd Nov. 19, 1940 2,471,393 Caldwell et al May 24, 1949 2,531,200 Davis Nov. 21, 1950 

